scholarly journals A general role for MIA3/TANGO1 in secretory pathway organization and function

2021 ◽  
Author(s):  
Janine McCaughey ◽  
Nicola L. Stevenson ◽  
Judith M. Mantell ◽  
Chris R. Neal ◽  
Alex Paterson ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Genome Engineering ◽  
General Role ◽  
Early Secretory Pathway ◽  
Pathway Gene ◽  
Gene And Protein Expression ◽  
Genomics And Proteomics ◽  
Cell Organization ◽  
And Function ◽  
Golgi Organization

Complex machinery is required to drive secretory cargo export from the endoplasmic reticulum, an essential process in eukaryotic cells. In vertebrates, the Mia3 gene encodes two major forms of Transport ANd Golgi Organization Protein 1 (TANGO1S and TANGO1L), previously implicated in selective trafficking of procollagen. Using genome engineering of human cells, light microscopy, secretion assays, genomics, and proteomics we show that disruption of the longer form, TANGO1L, results in relatively minor defects in secretory pathway organization and function including limited impacts on procollagen secretion. In contrast, loss of both long and short forms results in major defects in cell organization and secretion. These include a failure to maintain the localization of ERGIC53 and SURF4 to the ER-Golgi Intermediate Compartment and dramatic changes to the ultrastructure of the ER-Golgi interface. Disruption of TANGO1 causes significant changes in early secretory pathway gene and protein expression, and impairs secretion not only of large proteins, but of all types of secretory cargo including small soluble proteins. Our data support a general role for Mia3/TANGO1 in maintaining secretory pathway structure and function in vertebrate cells.

scholarly journals MIA3/TANGO1 enables efficient secretion by constraining COPII vesicle budding

2021 ◽  
Author(s):  
Janine McCaughey ◽  
Judith M. Mantell ◽  
Chris R. Neal ◽  
Kate Heesom ◽  
David J. Stephens
Keyword(s):  
Endoplasmic Reticulum ◽  
Light Microscopy ◽  
Secretory Pathway ◽  
Genome Engineering ◽  
High Volume ◽  
Vesicle Budding ◽  
Early Secretory Pathway ◽  
Copii Vesicle ◽  
Intermediate Compartment ◽  
Golgi Organization

AbstractComplex machinery is required to drive secretory cargo export from the endoplasmic reticulum. In vertebrates, this includes transport and Golgi organization protein 1 (TANGO1), encoded by the Mia3 gene. Here, using genome engineering of human cells light microscopy, secretion assays, and proteomics, we show loss of Mia3/TANGO1 results in formation of numerous vesicles and a loss of early secretory pathway integrity. This restricts secretion not only of large proteins like procollagens but of all types of secretory cargo. Our data shows that Mia3/TANGO1 constrains the propensity of COPII to form vesicles promoting instead the formation of the ER-Golgi intermediate compartment. Thus, Mia3/TANGO1 facilities the secretion of complex and high volume cargoes from vertebrate cells.

scholarly journals Membrane-Bound Meet Membraneless in Health and Disease

Cells ◽  
2019 ◽  
Vol 8 (9) ◽  
pp. 1000 ◽  
Author(s):  
Chujun Zhang ◽  
Catherine Rabouille
Keyword(s):  
Phase Separation ◽  
Membrane Trafficking ◽  
Secretory Pathway ◽  
Dependent Manner ◽  
P Bodies ◽  
Early Secretory Pathway ◽  
Cell Organization ◽  
Health And Disease ◽  
Membrane Bound ◽  
And Function

Membraneless organelles (MLOs) are defined as cellular structures that are not sealed by a lipidic membrane and are shown to form by phase separation. They exist in both the nucleus and the cytoplasm that is also heavily populated by numerous membrane-bound organelles. Even though the name membraneless suggests that MLOs are free of membrane, both membrane and factors regulating membrane trafficking steps are emerging as important components of MLO formation and function. As a result, we name them biocondensates. In this review, we examine the relationships between biocondensates and membrane. First, inhibition of membrane trafficking in the early secretory pathway leads to the formation of biocondensates (P-bodies and Sec bodies). In the same vein, stress granules have a complex relationship with the cyto-nuclear transport machinery. Second, membrane contributes to the regulated formation of phase separation in the cells and we will present examples including clustering at the plasma membrane and at the synapse. Finally, the whole cell appears to transit from an interphase phase-separated state to a mitotic diffuse state in a DYRK3 dependent manner. This firmly establishes a crosstalk between the two types of cell organization that will need to be further explored.

Illuminating cellular structure and function in the early secretory pathway by multispectral 3D imaging in living cells

2000 ◽  
Author(s):  
Jens Rietdorf ◽  
David J. Stephens ◽  
Anthony Squire ◽  
Jeremy Simpson ◽  
David T. Shima ◽  
...  
Keyword(s):  
Cellular Structure ◽  
3D Imaging ◽  
Secretory Pathway ◽  
Living Cells ◽  
Structure And Function ◽  
Early Secretory Pathway ◽  
And Function

scholarly journals A Novel Group of Glutaredoxins in the cis-Golgi Critical for Oxidative Stress Resistance

2008 ◽  
Vol 19 (6) ◽  
pp. 2673-2680 ◽  
Author(s):  
Nikola Mesecke ◽  
Anne Spang ◽  
Marcel Deponte ◽  
Johannes M. Herrmann
Keyword(s):  
Disulfide Bonds ◽  
Secretory Pathway ◽  
Reduced Glutathione ◽  
General Role ◽  
Growth Defects ◽  
Early Secretory Pathway ◽  
Full Complement ◽  
Increased Sensitivity ◽  
Substrate Proteins

Glutaredoxins represent a ubiquitous family of proteins that catalyze the reduction of disulfide bonds in their substrate proteins by use of reduced glutathione. In an attempt to identify the full complement of glutaredoxins in baker's yeast, we found three so-far uncharacterized glutaredoxin-like proteins that we named Grx6, Grx7, and Grx8. Grx6 and Grx7 represent closely related monothiol glutaredoxins that are synthesized with N-terminal signal sequences. Both proteins are located in the cis-Golgi, thereby representing the first glutaredoxins found in a compartment of the secretory pathway. In contrast to formerly described monothiol glutaredoxins, Grx6 and Grx7, showed a high glutaredoxin activity in vitro. Grx6 and Grx7 overlap in their activity and deletion mutants lacking both proteins show growth defects and a strongly increased sensitivity toward oxidizing agents such as hydrogen peroxide or diamide. Our observations suggest that Grx6 and Grx7 do not play a general role in the oxidative folding of proteins in the early secretory pathway but rather counteract the oxidation of specific thiol groups in substrate proteins.

scholarly journals Molecular basis for KDEL-mediated retrieval of escaped ER-resident proteins – SWEET talking the COPs

2020 ◽  
Vol 133 (19) ◽  
pp. jcs250100
Author(s):  
Simon Newstead ◽  
Francis Barr
Keyword(s):  
Secretory Pathway ◽  
Signal Sequence ◽  
Structural Similarity ◽  
Retrograde Transport ◽  
Coated Vesicles ◽  
Early Secretory Pathway ◽  
Cargo Proteins ◽  
Protein Localisation ◽  
And Function ◽  
Trafficking Receptor

ABSTRACTProtein localisation in the cell is controlled through the function of trafficking receptors, which recognise specific signal sequences and direct cargo proteins to different locations. The KDEL receptor (KDELR) was one of the first intracellular trafficking receptors identified and plays an essential role in maintaining the integrity of the early secretory pathway. The receptor recognises variants of a canonical C-terminal Lys-Asp-Glu-Leu (KDEL) signal sequence on ER-resident proteins when these escape to the Golgi, and targets these proteins to COPI- coated vesicles for retrograde transport back to the ER. The empty receptor is then recycled from the ER back to the Golgi by COPII-coated vesicles. Crystal structures of the KDELR show that it is structurally related to the PQ-loop family of transporters that are found in both pro- and eukaryotes, and shuttle sugars, amino acids and vitamins across cellular membranes. Furthermore, analogous to PQ-loop transporters, the KDELR undergoes a pH-dependent and ligand-regulated conformational cycle. Here, we propose that the striking structural similarity between the KDELR and PQ-loop transporters reveals a connection between transport and trafficking in the cell, with important implications for understanding trafficking receptor evolution and function.

scholarly journals δ-COP contains a helix C-terminal to its longin domain key to COPI dynamics and function

2016 ◽  
Vol 113 (25) ◽  
pp. 6916-6921 ◽  
Author(s):  
Eric C. Arakel ◽  
Kora P. Richter ◽  
Anne Clancy ◽  
Blanche Schwappach
Keyword(s):  
Secretory Pathway ◽  
Conformational Dynamics ◽  
Functional Complementation ◽  
Vesicle Formation ◽  
Membrane Recruitment ◽  
Early Secretory Pathway ◽  
Packing Defects ◽  
Clathrin Adaptor ◽  
Dynamics And Function ◽  
And Function

Membrane recruitment of coatomer and formation of coat protein I (COPI)-coated vesicles is crucial to homeostasis in the early secretory pathway. The conformational dynamics of COPI during cargo capture and vesicle formation is incompletely understood. By scanning the length of δ-COP via functional complementation in yeast, we dissect the domains of the δ-COP subunit. We show that the μ-homology domain is dispensable for COPI function in the early secretory pathway, whereas the N-terminal longin domain is essential. We map a previously uncharacterized helix, C-terminal to the longin domain, that is specifically required for the retrieval of HDEL-bearing endoplasmic reticulum-luminal residents. It is positionally analogous to an unstructured linker that becomes helical and membrane-facing in the open form of the AP2 clathrin adaptor complex. Based on the amphipathic nature of the critical helix it may probe the membrane for lipid packing defects or mediate interaction with cargo and thus contribute to stabilizing membrane-associated coatomer.

scholarly journals Sphingomyelin synthase-related protein SMSr controls ceramide homeostasis in the ER

2009 ◽  
Vol 185 (6) ◽  
pp. 1013-1027 ◽  
Author(s):  
Ana M. Vacaru ◽  
Fikadu G. Tafesse ◽  
Philipp Ternes ◽  
Vangelis Kondylis ◽  
Martin Hermansson ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Pathway ◽  
Sphingolipid Metabolism ◽  
Related Protein ◽  
Sphingomyelin Synthase ◽  
Transfer Protein ◽  
Early Secretory Pathway ◽  
Cell Organization ◽  
Ceramide Accumulation ◽  
Substantial Rise

Ceramides are central intermediates of sphingolipid metabolism with critical functions in cell organization and survival. They are synthesized on the cytosolic surface of the endoplasmic reticulum (ER) and transported by ceramide transfer protein to the Golgi for conversion to sphingomyelin (SM) by SM synthase SMS1. In this study, we report the identification of an SMS1-related (SMSr) enzyme, which catalyses the synthesis of the SM analogue ceramide phosphoethanolamine (CPE) in the ER lumen. Strikingly, SMSr produces only trace amounts of CPE, i.e., 300-fold less than SMS1-derived SM. Nevertheless, blocking its catalytic activity causes a substantial rise in ER ceramide levels and a structural collapse of the early secretory pathway. We find that the latter phenotype is not caused by depletion of CPE but rather a consequence of ceramide accumulation in the ER. Our results establish SMSr as a key regulator of ceramide homeostasis that seems to operate as a sensor rather than a converter of ceramides in the ER.

scholarly journals Structure and mechanism of TRAPPIII-mediated Rab1 activation

2020 ◽  
Author(s):  
Aaron M.N. Joiner ◽  
Ben P. Phillips ◽  
Kumar Yugandhar ◽  
Ethan J. Sanford ◽  
Marcus B. Smolka ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Membrane Surface ◽  
Regulatory Subunit ◽  
Amphipathic Helix ◽  
Nucleotide Exchange ◽  
Early Secretory Pathway ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Α Helix ◽  
And Function

ABSTRACTThe GTPase Rab1 is a master regulator of both the early secretory pathway and autophagy. Rab1 activation is controlled by its GEF (guanine nucleotide exchange factor), the multi-subunit TRAPPIII complex. The Trs85 regulatory subunit is critical for robust activation of Rab1 but its mechanistic role within the complex has remained unclear. Here we report the cryo-EM structure of the intact yeast TRAPPIII complex bound to its substrate Rab1/Ypt1. The orientation of the Rab1/Ypt1 hypervariable domain when bound to the complex leads to a model for how TRAPPIII associates with and activates Rab1/Ypt1 at the membrane surface. We identify a conserved amphipathic α-helix motif within Trs85 and demonstrate that this helix is required for stable membrane binding and Rab1/Ypt1 activation by TRAPPIII. Taken together, our results provide a comprehensive analysis of the structure and function of the yeast TRAPPIII complex and reveal that the key function of Trs85 is to serve as a membrane anchor, via its amphipathic helix, for the entire TRAPPIII complex.

scholarly journals The E3 ubiquitin ligase MARCH2 regulates ERGIC3-dependent trafficking of secretory proteins

2019 ◽  
Vol 294 (28) ◽  
pp. 10900-10912 ◽  
Author(s):  
Wonjin Yoo ◽  
Eun-Bee Cho ◽  
Sungjoo Kim ◽  
Jong-Bok Yoon
Keyword(s):  
Ubiquitin Ligase ◽  
Protein Trafficking ◽  
Secretory Pathway ◽  
E3 Ubiquitin Ligase ◽  
Secretory Proteins ◽  
Early Secretory Pathway ◽  
Cargo Proteins ◽  
Lysine Residues ◽  
Subsequent Degradation ◽  
And Function

The E3 ubiquitin ligase membrane-associated ring-CH–type finger 2 (MARCH2) is known to be involved in intracellular vesicular trafficking, but its role in the early secretory pathway between the endoplasmic reticulum (ER) and Golgi compartments is largely unknown. Human ER–Golgi intermediate compartment protein 2 (ERGIC2) and ERGIC3 are orthologs of Erv41 and Erv46 in yeast, proteins that form a heteromeric complex, cycle between the ER and Golgi, and function as cargo receptors in both anterograde and retrograde protein trafficking. Here, we report that MARCH2 directs ubiquitination and subsequent degradation of ERGIC3 and that MARCH2 depletion increases endogenous ERGIC3 levels. We provide evidence that the lysine residues at positions 6 and 8 of ERGIC3 are the major sites of MARCH2-mediated ubiquitination. Of note, MARCH2 did not significantly decrease the levels of an ERGIC3 variant with lysine-to-arginine substitutions at residues 6 and 8. We also show that ERGIC3 binds to itself or to ERGIC2, whereas ERGIC2 is unable to interact with itself. Our results indicate that α1-antitrypsin and haptoglobin are likely to be cargo proteins of ERGIC3. We further observed that α1-antitrypsin and haptoglobin specifically bind to ERGIC3 and that ERGIC3 depletion decreases their secretion. Moreover, MARCH2 reduced secretion of α1-antitrypsin and haptoglobin, and coexpression of the ubiquitination-resistant ERGIC3 variant largely restored their secretion, suggesting that MARCH2-mediated ERGIC3 ubiquitination is the major cause of the decrease in trafficking of ERGIC3-binding secretory proteins. Our findings provide detailed insights into the regulation of the early secretory pathway by MARCH2 and into ERGIC3 function.

scholarly journals Vesicular Calcium Regulates Coat Retention, Fusogenicity, and Size of Pre-Golgi Intermediates

2010 ◽  
Vol 21 (6) ◽  
pp. 1033-1046 ◽  
Author(s):  
Marvin Bentley ◽  
Deborah C. Nycz ◽  
Ashwini Joglekar ◽  
Ismene Fertschai ◽  
Roland Malli ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Rat Kidney ◽  
Cyclopiazonic Acid ◽  
Early Secretory Pathway ◽  
Shell Protein ◽  
Ef Hand ◽  
Copii Vesicle ◽  
Normal Rat ◽  
And Function

The significance and extent of Ca2+ regulation of the biosynthetic secretory pathway have been difficult to establish, and our knowledge of regulatory relationships integrating Ca2+ with vesicle coats and function is rudimentary. Here, we investigated potential roles and mechanisms of luminal Ca2+ in the early secretory pathway. Specific depletion of luminal Ca2+ in living normal rat kidney cells using cyclopiazonic acid (CPA) resulted in the extreme expansion of vesicular tubular cluster (VTC) elements. Consistent with this, a suppressive role for vesicle-associated Ca2+ in COPII vesicle homotypic fusion was demonstrated in vitro using Ca2+ chelators. The EF-hand–containing protein apoptosis-linked gene 2 (ALG-2), previously implicated in the stabilization of sec31 at endoplasmic reticulum exit sites, inhibited COPII vesicle fusion in a Ca2+-requiring manner, suggesting that ALG-2 may be a sensor for the effects of vesicular Ca2+ on homotypic fusion. Immunoisolation established that Ca2+ chelation inhibits and ALG-2 specifically favors residual retention of the COPII outer shell protein sec31 on pre-Golgi fusion intermediates. We conclude that vesicle-associated Ca2+, acting through ALG-2, favors the retention of residual coat molecules that seem to suppress membrane fusion. We propose that in cells, these Ca2+-dependent mechanisms temporally regulate COPII vesicle interactions, VTC biogenesis, cargo sorting, and VTC maturation.

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